Induction motor



April 12, 1955 KAZAN 2,706,269

INDUCTION MOTOR Filed June 4, 1951 2 Sheets-Sheet 1 FIG. I

C L L C ATT. SECTION ENERs 0 OL/ FIG-4 INVENTOR. BENJAMIN KAZAN April 12, 1955 Filed June 4. 1951 B. KAZAN moucnou MOTOR 2 Sheets-Sheet 2 TERMINATING LOAD .TERMIN ATING LOAD INVENTOR.

BENJAMIN KAZAN United States Patent INDUCTION MOTOR Benjamin Kazan, Long Branch, N. J.

Application June 4, 1951, Serial No. 229,859

1 Claim. (Cl. 318-220) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to travelling wave systems and more particularly to apparatus adapted for use in travelling wave systems to generate radio frequency energy directly from mechanical energy or to convert radio frequency energy into mechanical energy.

In conventional travelling wave tube amplifiers, a radio frequency wave is amplified by the interaction of an electron beam with the electromagnetic field propagated along a phase delaying structure such as a helix, or with a second electron beam of different velocity. In this type of tube, the amplified wave obtains its energy from the direct-current power supplied to the electron beam.

It is well known that the small signal behavior of long electron beams may be analyzed in terms of propagating space-charge waves. Thus, a high voltage beam may be considered to be equivalent to a high pass transmission line moving at the average beam velocity. Such electron beams, therefore, may be replaced by suitable phase delaying networks made of metal or solid dielectric material moving relative to each other. Thus, by employing two electrical networks which interact with each other so that a radio frequency wave established on both will have the proper phase velocity on one transmission line with respect to the other, amplification of a radio frequency wave may be achieved. When two such interacting electrical networks are employed, however, the growing, or amplified, radio frequency wave receives its energy from the mechanical work done in moving one network with respect to the other. A system as described above is shown in the patent of Cutler et al., Serial No. 2,608,623, issued August 26, 1952.

One type of phase delaying network which may be employed in such a system is a filter-type transmission line having successive inductive elements mounted in the form of a ring. The input and output ends of such a transmission line may be suitably isolated from each other to prevent direct coupling. If a radio-frequency signal within the pass band of the filter-type transmission line is applied to the input end thereof, a current wave will be propagated down the filter toward the output end which may be assumed to be matched. A magnetic field, more or less sinusoidal with distance, will thus be produced and this wave will be propagated along with the current wave. Although the propagating magnetic field may be attenu ated with distance along the filter-type transmission line due to losses in the line elements, it will travel around the filter in a manner somewhat analogous to the rotating magnetic field produced by the stator winding of a conventional polyphase induction motor.

If the ring-like filter network is provided with a centrally positioned rotor similar to that of an induction motor, i. e., consisting of a number of shorted inductive elements, the travelling magnetic wave will induce radio frequency currents in the rotor coils, to provide a mechanical force for driving the rotor. The device is thus capable of converting radio frequency energy into mechanical energy.

However, as in the case of an induction motor, when the rotor is mechanically driven at speeds in excess of the rotating magnetic field, such a device is capable of generating radio frequency energy. This is equivalent to stating that, at such rotor speeds, the stator coils have an effective resistance which is negative. In other words, if

2,706,269 Patented Apr. 12, 1955 'ice the centrally positioned rotor is driven at a proper speed in excess of the propagated travelling magnetic wave, each coil of the filter network will have a resistance which is effectively negative. As a result, the propagating radio frequency current wave in the filter network will, instead of being attenuated, grow larger, or be amplified as it approaches the output end. The device thus may also be considered to be a four-terminal network capable of amplifying input signals over a range of frequencies for a given rotor speed. Reflected waves due to improper termination of the filter, i. e., waves travelling in the direction opposite to the motion of the rotor, are not amplified, but attenuated, so that a high gain in the forward direction does not require an unduly good match at the output end to prevent oscillations.

It is an object of the present invention, therefore, to provide a travelling wave system wherein radio frequency energy is converted into mechanical energy.

It is another object of this invention to provide a mechanical alternating current amplifier by utilizing phase delaying networks adapted to move relatively with each other.

It is still another object of the present invention to provide a travelling wave system wherein mechanical energy is converted into radio frequency energy.

It is yet another object of the invention to provide a rotating or travelling vector of alternating voltage and current to produce mechanical motion.

It is still another object of the present invention to provide amplification of A.-C. and R.-F. signals without the use of vacuum tubes or semiconductors.

In accordance with the present invention, the travelling wave system comprises a source of radio-frequency or alternating current energy, a stator including a phase delaying network, and a rotor network closely coupled to said stator network. The radio frequency energy is propagated in one direction only along the inner edge of the stator phase delaying network as a travelling electromagnetic wave at a predetermined velocity. A substantially sinusoidal magnetic field is thus propagated along the stator. As the sinusoidal magnetic field moves around the stator network, it tends to pull the rotor in the same direction, thereby producing motor action. If, however, the rotor network is mechanically driven in a direction opposing the initial direction of rotation as a motor at a speed in excess of the rotating magnetic field, amplification of the radio frequency signal may be achieved. To prevent feedback from the output of the phase delaying network to the input thereof, shielding means are provided therebetween.

For a better understanding of the present invention, together with further and other objects thereof, reference is had to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a block schematic diagram of a travelling Wave system in accordance with the invention;

Figures 2 and 3 illustrate preferred embodiments of the invention for use with relatively low frequencies; and

Figure 4 illustrates a preferred embodiment of the invention for use with microwave frequencies.

Referring now to Figure 1 of the drawings, there is shown at 2 a phase delaying stator network, capable of propagating an A.-C. or radio frequency wave in one direction, mounted in the form of a ring and having discrete input terminals 4, 6 and discrete output terminals 8, 10. It is to be understood, of course, that the input and output terminals of said stator network are suitably isolated to prevent direct coupling. For radio frequencies, phase delay network 2 may include any of the well known high frequency transmission line structures, such as travelling wave tube type of helix or a resonant type of magnetron anode block. For relatively low frequencies A.-C. for example, stator network 2 may comprise a conventional lumped circuit delay line utilized in low frequency techniques. The distributed inductive and capacitive parameters of such transmission lines may be represented by stator elements L and C respectively. Output terminals 8, 10 are terminated by a load 12 which is assumed to match the characteristic impedances of the phase delaying network. The output of a radio frequency 3 or A.C. energy source 14 is applied to input terminals 4, 6, as shown.

Closely coupled to stator network 2 and concentrically positioned therewith is rotor network 16 which may comprise a series of shorted inductive elements represented by Numerous other forms for rotor network 16 may also be provided. For example, rotor network 16 may consist of a continuous copper drum or a lumped circuit delay line including both capacitive and inductive elements similar in construction to the stator network for propagating a radio frequency or A.C. wave. In the latter case, suitably related propagation constants for the stator and rotor networks which differ by small amounts may enable the generation of a growing wave without the necessity of driving rotor network 16 at mechanical speeds in excess of the travelling wave propagated along the inner edge of phase delaying stator network 2. In order to prevent feedback from the output and input circuits, an attenuating section 18 may be provided therebetween, as shown. By this arrangement, radio or A.C. frequency energy induced in the rotor will exist thereon only along thaat portion of the rotor network periphery which is coextensive with the stator network.

Figures 2 and 3 illustrate a preferred embodiment of my invention for use at relatively low frequencies. As shown, stator network 2 comprises a conventional lumped circuit delay line with successive inductive elements 20, mounted in the form of a ring and having discrete input terminals 4, 6 and discrete output terminals 8, 10. Capacitive elements 24 may be grounded as at 26. The winding of rotor 16, which may be of conventional construction similar to that of a 60 cycle A.C. induction motor, is closely coupled to the inductive elements of stator network 2. Attenuating circuit 18 may comprise several serially connected high loss sections, each section including a coil 28 connected in parallel with a resistor 30. As previously explained, rotor 16 may also comprise a lumped circuit delay line similar in construction to the stator network. An A.C. source 32 is applied to input terminals 4, 6. Output terminals 8, are terminated by load 12 which is assumed to match the characteristic impedance of the lumped delay line.

In Figure 3, rings 34 and 36, made of iron or other suitable high permeability material, are respectively provided for stator network 2 and rotor network 16 to increase the magnetic flux. The construction of said stator and rotor rings are conventional and may be identical to the stator and rotor rings employed in A.C. induction motors.

In the arrangement described in Figures 2 and 3 one of the primary problems is that of obtaining a filter network whose phase velocity is sufiiciently low so that a rotor, whose linear velocity exceeds this phase velocity, could be conveniently driven. Assuming that rotor speeds of several thousand R. P. M. were desired and that approximately 30 coils were employed for the filter ring, the coils would have to be of the order of one henry and the condensers one microfarad, for example, thus restricting the operation of the filter to audio frequencies.

Figure 4 illustrates an embodiment of my invention for microwave frequencies. As shown, stator phase delay network 2 comprises a slot-and-hole resonant type structure formed in the shape of a ring and having discrete input and output circuits, as illustrated at 40 and 42 respectively. It is to be assumed that the input and output circuits are suitably matched. As mentioned hereinabove, radio frequency waves starting from input circuit 40 should be able to propagate in one direction only. Similarly, it is desirable that the radio frequency wave traverse the path between the input and output circuits. These conditions are fulfilled by providing a suitable shield, which is well known in the art, between input circuit 40 and output circuit 42. Such a shield is shown diagrammatically in Figure 4 by dashed line 44. Rotor 16 may consist of a continual copper drum which is concentrically positioned with the slotted hole ring-like structure. It is to be understood of course that other well known magnetron anode block resonant structures may be used as the stator phase delay network.

Another stator, not shown, which may be employed as a stator wave delay network at high radio frequencies is a circular helix wound in the shape of a ring and having discrete input and output terminals. A suitable 1rloior may be concentrically positioned with respect to the In operation, the travelling magnetic field vector is propagated around the iner periphery of stator and thus induces a current in the rotor which in turn interacts with the magnetic field to provide mechanical motion of the rotor. Thus, within the frequency region of transmission of the stator and rotor delay lines, any A.C. frequency may be used for producing mechanical energy of rotation. If the rotor is mechanically driven in a direction opposing the initial direction of rotation as a motor at speeds in excess of the rotating magnetic field, amplification of the travelling stator wave will be achieved.

The device described hereinabove may also operate as a power measuring device since the rotational or translational force will be proportional to the power flowing along the travelling wave stator. The power may be indicated by the displacement of the rotor or moving element which may be provided with a conventional spring element to provide a restoring force.

While there has been described What is at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein Without departing from the invention, and it is, therefore, aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

In a travelling wave system for converting alternating current energy into mechanical energy, a stator comprising a phase delaying network having discrete input and output terminals, means for applying said alternating current energy to said input terminals whereby a rotating magnetic field is propagated along the inner edge of said phase delaying network, a terminating load connected to said output terminal for matching the characteristic impedance of the phase delaying network whereby the applied energy is propagated in only one direction, attenuating means between the input and output terminals for preventing feedback between said terminals, a rotor network comprising a series of shorted inducted elements in coupling relationship with said stator, said rotor net work being concentrically spaced with respect to said stator network and rotated in response to the rotating magnetic field.

References Cited in the file of this patent UNITED STATES PATENTS 2,608,623 Cutler et a1. Aug. 26, 1952 

